Method of producing bus bars for centralized power distribution unit

ABSTRACT

A centralized power distribution unit for a vehicular thin brushless motor includes a plurality of bus bars and a resin insulating layer that covers the bus bars. The bus bars are disposed correspondingly with phases of the motor. Each of the bus bars has a terminal portion to be connected to a battery and one or more tabs to be connected respectively to one or more windings of a stator. Each of the bus bars is shaped into a substantially annular shape by bending a molded material in a thickness direction. The molded material is obtained by stamping out a conductive metal plate into a strip-like shape. Diameters of the annular shapes of the bus bars are set to be different from one another depending on the corresponding phase of the motor. The bus bars are stacked in a radial direction of the centralized power distribution unit, mutually separated by a predetermined gap.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The present invention relates to a centralized power distributionunit which is used for performing centralized power distribution onstator windings of a vehicular thin brushless motor.

[0003] 2. Description of Related Art

[0004] Recently, automobiles with good fuel economy have been in highdemand. As one example of automobile manufacturers' efforts to meetthese demands, hybrid cars with super low fuel consumption have beendeveloped. In particular, a hybrid car has been proposed recently whichis provided with an auxiliary power mechanism (a motor assist mechanism)in which an engine provides the main power and a DC brushless motorassists the engine upon acceleration or the like.

[0005] The motor assist mechanism is subject to much constraint ininstallation, since a brushless motor constituting the motor assistmechanism is disposed in a limited space, for example, a space betweenan engine and a transmission in an engine compartment. Thus, such abrushless motor is required to have a thin configuration.

[0006] A thin brushless motor to be used in the motor assist mechanismof a vehicle includes a rotor directly connected to a crankshaft of theengine, and a ring-like stator enclosing the rotor. The stator includesmany magnetic poles that have windings on cores, a stator holder thatcontains the magnetic poles, and a centralized distribution unit thatconcentratedly distributes currents to the windings.

[0007] As shown in FIG. 34A, a conventional centralized powerdistribution unit used in a three-phase DC brushless motor includesthree ring-like bus bars 101, 102, and 103. Each of the ring-like busbars 101, 102, and 103 includes a ring-like body 104, a terminal portion105 projecting outwardly in a radial direction on an outer periphery ofthe ring-like body 104, and a plurality of tabs 106 each projectinginwardly in the radial direction on an inner periphery of the ring-likebody 104. Each terminal portion 105 is electrically connected through anelectric wire to a battery while each tab 106 is electrically connectedthrough a respective electric wire to an end of a respective winding.When the three ring-like bus bars 101, 102, and 103 are energized,currents are concentratedly distributed to the windings corresponding toa U phase, a V phase, and a W phase. Consequently, the motor is driven.

SUMMARY OF THE INVENTION

[0008] When the conventional centralized power distribution unit is tobe produced, press moldings must be conducted on a conductive metalplate 107 using different molds to form ring-like bus bars 101, 102, and103 for the three phases as shown in FIG. 34B.

[0009] In order to obtain the ring-like bus bars 101, 102, and 103, theconductive metal plate 107 must have a size which is at least as largerthan the outer diameters of the bus bars 101, 102, and 103. Most of theportions of the metal plate other than the portions which are stampedout into the ring-like shape become wasted. Therefore, conventionally,as seen from the above, the conductive metal plate 107 includes a verylarge useless portion and hence is wasteful. This is a cause ofincreased production costs of a centralized power distribution unit.

[0010] The invention has been made in view of the above-discussedproblem. It is an object of the invention to provide a centralized powerdistribution unit for a vehicular thin brushless motor which can beproduced at a small amount of waste of a metal material and at a lowcost. It is another object of the invention to provide a method ofproducing bus bars which are preferably used as excellent components ofthe centralized power distribution unit.

[0011] In order to attain these objects, in the invention, a centralizedpower distribution unit for a vehicular thin brushless motor includes: aplurality of bus bars each having a terminal portion to be connected toa battery, and tabs to be respectively connected to windings of astator, the bus bars being disposed correspondingly with phases of themotor; and a resin insulating layer that covers the bus bars. Thecentralized power distribution unit can intensively distribute a currentto the windings, and has a ring-like shape. Each of the bus bars isshaped into a substantially annular shape by bending a molded materialwhich is obtained by stamping out a conductive metal plate into astrip-like shape. In a thickness direction, diameters of the bus barsare set to be different from one another depending on the phase, and thebus bars are stacked in a radial direction of the centralized powerdistribution unit, being separated from one another by a predeterminedgap.

[0012] According to the invention, therefore, the bus bars can beconfigured by materials which are stamped out into a strip-like shape,so that it is not required to use a considerably large conductive metalplate and the bus bars can be obtained with a reduced amount of wastedmaterial. In the case of a strip-like shape, the bus bars can beobtained in a state where the bus bars are densely placed, and hence theamount of wasted material can be reduced. Therefore, the material costof the bus bars can be reduced, with the result that the centralizedpower distribution unit can be produced at a low cost.

[0013] In the invention, in a method of producing bus bars used in acentralized power distribution unit of the above-mentioned invention,press molding using a mold is conducted to simultaneously stamp out thebus bars respectively corresponding to the phases from a commonconductive metal plate.

[0014] According to the invention, therefore, the material loss isremarkably reduced as compared with that in a conventional method.Therefore, the material cost of the bus bars can be reduced, and thecost of the mold can be lowered. As a result, the centralized powerdistribution unit can be produced at a low cost.

[0015] Preferably, when a linear bus bar body is stamped out by thepress molding, the terminal portion and the tabs are integrally formedin a state where the terminal portion and the tabs are coupled to thebus bar body. In this case, a step of welding or the like is notnecessary, and hence the production cost can be reduced as compared withthe case where a terminal portion and tabs which are previously producedare later attached to the bus bar body. Therefore, the use of such busbars enables the centralized power distribution unit to be produced at alow cost.

[0016] Preferably, the bus bars are stamped out in a state where the busbar bodies are placed in parallel, and in a state where both ends of thebus bar bodies are substantially aligned with one another. According tothe configuration, the material loss in the stamping process is reduced,so that further cost reduction can be attained.

[0017] Preferably, when the bus bars are laid out in parallel in a rowon a conductive metal plate in order to be stamped from the conductivemetal plate, the terminal portion and the tabs of one(s) of the bus barswhich is (are) positioned at an outermost side(s) are directed to acenter of the bus bar row. In this case, a conductive metal plate of asmaller width can be used as compared with the case where the terminalportion and tabs of the outermost one(s) of the bus bars are directed tothe outer side of the bus bar row. Therefore, the material loss in thestamping process is further reduced, so that still further costreduction can be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The foregoing and other features of the present invention willbecome apparent to one skilled in the art to which the present inventionrelates upon consideration of the invention with reference to theaccompanying drawings, wherein:

[0019]FIG. 1 is a schematic side elevation view of a thin brushlessmotor;

[0020]FIG. 2 is a schematic wiring diagram of the thin brushless motor;

[0021]FIG. 3 is a perspective view of a centralized distribution unit;

[0022]FIG. 4 is a front elevation view of the centralized distributionunit;

[0023]FIG. 5 is a rear elevation view of the centralized distributionunit;

[0024]FIG. 6A is a cross sectional view of the centralized distributionunit;

[0025]FIG. 6B is an enlarged cross sectional view of a terminal portionof the unit;

[0026]FIG. 6C is an enlarged perspective view of the terminal portionshown in FIG. 6B;

[0027]FIG. 7 is a plan elevation view of a terminal portion of thecentralized distribution unit;

[0028]FIG. 8 is a perspective view of an insulating holder;

[0029]FIG. 9 is a front elevation view of the insulating holder in whichbus bars are inserted;

[0030]FIG. 10 is an enlarged front elevation view of a part of theinsulating holder;

[0031]FIG. 11 is a front elevation view of bus bars from which theinsulating holder is omitted;

[0032]FIG. 12 is an enlarged front elevation view of a part of theinsulating holder, illustrating a bus bar non-containing section in theholder;

[0033]FIG. 13A is a cross sectional view of the insulating holder takenalong line 13 a-13 a in FIG. 9;

[0034]FIG. 13B is a cross sectional view of the insulating holder takenalong line 13 b-13 b in FIG. 9;

[0035]FIG. 13C is a cross sectional view of the insulating holder takenalong line 13 c-13 c in FIG. 9;

[0036]FIG. 14A is a cross sectional view of the centralized distributionunit taken along line 14 a-14 a in FIG. 4;

[0037]FIG. 14B is a perspective view of the centralized distributionunit shown in FIG. 14A;

[0038]FIG. 15A is a cross sectional view of the centralized distributionunit taken along line 15 a-15 a in FIG. 4;

[0039]FIG. 15B is a perspective view of the centralized distributionunit shown in FIG. 15A;

[0040]FIG. 16A is a cross sectional view of the centralized distributionunit taken along line 16 a-16 a in FIG. 4;

[0041]FIG. 16B is a perspective view of the centralized distributionunit shown in FIG. 16A;

[0042]FIG. 17A is a cross sectional view of the centralized distributionunit taken along line 17 a-17 a in FIG. 4;

[0043]FIG. 17B is a perspective view of the centralized distributionunit shown in FIG. 17A;

[0044]FIG. 18A is a cross sectional view of a first press apparatus,illustrating the apparatus in an open position;

[0045]FIG. 18B is a perspective view of a part of a strip-like blank tobe pressed by the first press apparatus shown in FIG. 18A;

[0046]FIG. 19A is a cross sectional view of the first press apparatus,illustrating the apparatus in a closed position;

[0047]FIG. 19B is a perspective view of a strip-like blank that has beenpressed in the first press apparatus shown in FIG. 19A;

[0048]FIG. 20A is a cross sectional view of a second press apparatus,illustrating the apparatus in an open position;

[0049]FIG. 20B is a perspective view of a strip-like blank that has beenpressed in the second press apparatus shown in FIG. 20A;

[0050]FIG. 21A is a plan elevation view of a strip-like blank,illustrating the blank in a state before a terminal portion of the busbar is bent;

[0051]FIG. 21B is a longitudinal sectional view of the blank taken alongline 21 b-21 b in FIG. 21B;

[0052]FIG. 22 is a rear elevation view of the insulating holder;

[0053]FIG. 23A is an enlarged plan elevation view of a bearing recess;

[0054]FIG. 23B is an enlarged perspective view of the bearing recessshown in FIG. 23A;

[0055]FIG. 24 is a cross sectional view of an insert-molding mold,illustrating the mold in which the insulating holder is set;

[0056]FIG. 25 is a cross sectional view of the insert-molding moldsimilar to FIG. 24, illustrating the mold into which a molten resinmaterial is poured;

[0057]FIG. 26 is a cross sectional view of the insert-molding moldsimilar to FIG. 25, illustrating the mold in which a holder support pinand an upper mold member support are retracted;

[0058]FIG. 27 is a cross sectional view of the insert-molding moldsimilar to FIG. 26, illustrating the mold in an open position;

[0059]FIG. 28 is a plan view of a conductive metallic plate to bepunched into the strip-like blanks, illustrating a process for producingthe centralized distribution unit;

[0060]FIG. 29 is a perspective view of the blanks shown in FIG. 28,illustrating the terminal portion of each of bus bars being bent;

[0061]FIG. 30 is a perspective view of ring-like blanks that are formedby bending the blanks shown in FIG. 29, illustrating the bus bars beinginserted into the insulating holder;

[0062]FIG. 31 is a perspective view of the blanks shown in FIG. 30,illustrating tabs of the bus bars being bent inward;

[0063]FIG. 32 is a perspective view of the blanks shown in FIG. 3 1,illustrating a part of the terminal portions being sealed by a sealingmaterial;

[0064]FIG. 33 is a view showing another example of a process of stampingout strip-like molded materials from a conductive metal plate;

[0065]FIG. 34A is a perspective view of conventional ring-like bus bars;and

[0066]FIG. 34B is a plan view of a conductive metallic plate from whichthe conventional ring-like bus bars are to be punched out.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0067] As shown in FIG. 1, a three-phase thin DC brushless motor 11 tobe used in a hybrid automobile is disposed between an engine 12 and atransmission 13. The thin DC brushless motor 11 includes a rotor 14connected, e.g., directly connected, to a crankshaft of the engine 12,and a ring-like stator 15 enclosing the rotor 14. The stator 15 includesa plurality of magnetic poles that have windings 16 on cores, a statorholder 18 that contains the magnetic poles, and an annular centralizeddistribution unit 17 that concentratedly distributes currents to thewindings 16.

[0068]FIG. 2 shows a schematic diagram of the stator 15. As shown inFIG. 2, an end of each phase winding 16 is connected to one of bus bars22 a, 22 b, and 22 c formed in the centralized distribution unit 17while the other end is connected to a ring-like conductive member (notshown).

[0069] As shown in FIGS. 3 to 6, a continuous annular insulating holder21 (FIGS. 6A and 6B) made of synthetic resin is embedded in thecentralized distribution unit 17. The insulating holder 21 may be madeof, for example, PBT (polybutyrene terephthalate), PPS (polyphenylenesulfide), or the like.

[0070] In this embodiment, the insulating holder 21 is made of a PPScontaining a glass fiber of 40% by weight. The reason why the insulatingholder 21 is made of such a material is that the material is superior inits electrical properties (dielectric strength). In particular, in thethin DC brushless motor 11 in the present embodiment, since voltages tobe applied to the respective phase bus bars 22 a, 22 b, and 22 c arehigh, it is important to maintain the dielectric strength in therespective bus bars 22 a, 22 b, and 22 c. The dielectric strength inthis case is required to be above 2000V. In addition, PPS has a highmechanical strength as well as a high heat resistance in comparison witha common resin such as a PP (polypropylene) or the like.

[0071] As shown in FIGS. 8, 9, and 10, the insulating holder 21 isprovided on one side with holding grooves 23 a, 23 b, and 23 c extendingin the circumferential direction. The holding grooves 23 a, 23 b, and 23c are disposed in parallel at a given distance in the radial directionof the insulating holder 21. The bus bars 22 a, 22 b, and 22 ccorresponding to the respective phases are individually inserted intothe respective holding grooves 23 a, 23 b, and 23 c, respectively. Therespective bus bars 22 a, 22 b, and 22 c are stacked on each other inthe radial direction of the centralized distribution unit 17 with thebus bars being spaced from each other at a given distance. Accordingly,the respective holding grooves 23 a, 23 b, and 23 c serve to hold therespective bus bars 22 a, 22 b, and 22 c in the precise positions. Theinsulating holder 21 and bus bars 22 a, 22 b, and 22 c are entirelycovered with a resin insulation layer 25. This covering accomplishesindividual insulation between the respective bus bars 22 a, 22 b, and 22c.

[0072] The resin insulation layer 25 is made of a PPS containing a glassfiber, similar to the insulating holder 21. The reason why this materialis used in the resin insulation layer 25 is that the material issuperior in its electric properties (dielectric strength), heatresistance, and mechanical strength, similar to the reason it is used inthe insulating holder 21. The material in the resin insulation layer 25utilizes a synthetic resin.

[0073] In this embodiment, the bus bar 22 a at the inside layercorresponds to a W phase, the bus bar 22 b at the intermediate layer toa U phase, and the bus bar 22 c at the outside layer to a V phase,respectively. For convenience of explanation, the W phase bus bar 22 ais referred to as the “inside bus bar 22 a” hereinafter, the U phase busbar 22 b as the “intermediate bus bar 22 b,” and the V phase bus bar 22c as the “outside bus bar 22 c,” respectively.

[0074] The respective bus bars 22 a, 22 b, and 22 c will be explainedbelow. The respective bus bars 22 a, 22 b, and 22 c are formedbeforehand by punching out a conductive metallic plate made of a copperor a copper alloy into a strip-like blank using a press apparatus, andbending the blank in the thickness direction to form a discontinuousannular configuration from which a part of an arc is removed(substantially a C-shape). The diameters of the respective bus bars 22a, 22 b, and 22 c are set to be larger in order from the inside layer tothe outside layer. The formed respective bus bars 22 a, 22 b, and 22 care inserted into the respective holding grooves 23 a, 23 b, and 23 c.This makes it easy to assemble the respective bus bars 22 a, 22 b, and22 c in the insulating holder 21.

[0075] As shown in FIGS. 8 to 11, the respective bus bars 22 a, 22 b,and 22 c are provided with respective pluralities of projecting tabs 41a, 41 b, and 41 c to which the respective windings 16 are connected. Therespective tabs 41 a, 41 b, and 42 c are punched out from the conductivemetallic plate simultaneously when the respective bus bars 22 a, 22 b,and 22 c are punched out from the plate by the press apparatus.Consequently, the respective bus bars 22 a, 22 b, and 22 c and therespective tabs 41 a, 41 b, and 41 c are formed integrally together asone piece by a single pressing step. This simplifies the productionprocess in comparison with a process in which the respective tabs 41 a,41 b, and 41 c are coupled to the respective bus bars 22 a, 22 b, and 22c by welding.

[0076] Six of each of tabs 41 a, 41 b, and 41 c are provided on therespective bus bars 22 a, 22 b, and 22 c. The respective tabs 41 a, 41b, and 41 c in the respective phase are arranged at an even angulardistance (i.e., 60 degrees with respect to the center) in thecircumferential direction of the respective bus bars 22 a, 22 b, and 22c. Removed portions 42 of the respective bus bars 22 a, 22 b, and 22 care displaced from each other by an angle of 20 degrees in thecircumferential direction. Consequently, eighteen of the tabs 41 a to 41c in total are arranged at an even angular distance of 20 degrees withrespect to the center in the circumferential direction of thecentralized distribution unit 17. As shown in FIG. 11, in the presentembodiment, in the case where the removed portion 42 of the outside busbar 22 c is set to be a reference, the intermediate bus bar 22 b isarranged away from the reference by +20 degrees in the clockwisedirection. Meanwhile, the inside bus bar 22 a is arranged away from thereference by −20 degrees in the counterclockwise direction.

[0077] The respective tabs 41 a, 41 b, and 41 c of the respective busbars 22 a, and 22 b, and 22 c are bent into L-shapes in cross section todirect the distal ends of them to the center of the centralizeddistribution unit 17.

[0078] Each distal end of the respective tabs 41 a, 41 b, and 41 cprojects inwardly in the radial direction from the inner periphery ofthe centralized distribution unit 17. Each winding 16 is connected to arespective projecting portion. The respective tabs 41 a, 41 b, and 41 care different in length. The distal end of each of the respective tabs41 a, 41 b, and 41 c is arranged on the same distance from the center ofthe centralized distribution unit 17. Accordingly, the respective tabs41 a, 41 b, and 41 c of the respective bus bars 22 a, 22 b, and 22 c arelonger in length in the radial direction of the centralized distributionunit in order from the inside bus bar 22 a to the outside bus bar 22 c.

[0079] As shown in FIGS. 15A and 15B, the tabs 41b of the intermediatebus bar 22 b are, at the section covered by the resin insulation layer25, provided with a curved portion 44 raised in the height direction ofthe walls 43 a, 43 b, 43 c, and 43 d that define the holding grooves 23a, 23 b, and 23 c. The curved portion 44 goes around the top side of theinside bus bar 22 a (i.e., another bus bar) in the resin insulationlayer 25. The curved portion 44 can provide an increased distancebetween the tabs 41 b and the adjacent bus bar.

[0080] As shown in FIGS. 16A and 16B, the tabs 41 c of the outside busbar 22 c are, at the section covered by the resin insulation layer 25provided with a curved portion 45 raised in the height direction of thewalls 43 a to 43 d. The curved portion 45 goes around the top sides ofthe intermediate bus bar 22 b as well as the inside bus bar 22 a (i.e.,other bus bars) in the resin insulation layer 25. The curved portion 45can provide an increased distance between the tabs 41 c and the adjacentbus bars. Since the curved portion 45 goes around two bus bars 22 a and22 b, the curved portion 45 is longer than the curved portion 44 of thetab 41 b on the intermediate bus bar 22 b.

[0081] As shown in FIGS. 14A and 14B, the tabs 41 a of the inside busbar 22 a have no curved portion on the proximal end, but rather have aright-angled portion. The tabs 41 a are not required to be at anincreased distance, since there is no adjacent bus bar for the tabs togo around.

[0082] As shown in FIGS. 14A and 14B, inside projecting pieces 47 areformed integrally with wall 43 b, and are positioned between tab formingsections of the inside bus bar 22 a from tab non-forming sections of theintermediate bus bar 22 b adjacent the inside bus bar 22 a. The insideprojecting pieces 47 can provide an increased creepage distance betweenthe inside bus bar 22 a and the intermediate bus bar 22 b adjacent theinside bus bar 22 a. Six inside projecting pieces 47 in total, made of asynthetic resin, are provided on the wall 43 b and arranged at an evenspacing in the circumferential direction of the insulating holder 21.The respective inside projecting pieces 47 correspond in position to therespective tabs 41 a formed on the inside bus bar 22 a. The portions ofwall 43 b having the inside projecting pieces 47 are higher than theportions of wall 43 b that space the tab non-forming sections of theinside bus bar 22 a and intermediate bus bar 22 b.

[0083] As shown in FIGS. 15A and 15B, an outside projecting piece 48 isformed integrally with wall 43 c that spaces a tab forming section ofthe intermediate bus bar 22 b from a tab non-forming section of theoutside bus bar 22 c adjacent the intermediate bus bar 22 b. The outsideprojecting piece 48 can provide an increased distance between theintermediate bus bar 22 b and the outside bus bar 22 c adjacent theintermediate bus bar 22 b. Six outside projecting pieces 48 in total,made of a synthetic resin, are provided on the wall 43 c and arranged atan even spacing in the circumferential direction of the insulatingholder 21. The respective outside projecting pieces 48 correspond to therespective tabs 41b formed on the intermediate bus bar 22 b. Theportions of wall 43 c having the outside projecting piece 48 are higherthan the portions of wall 43 c that space the tab non-forming sectionsof the intermediate bus bar 22 b and outside bus bar 22 c.

[0084] As shown in FIGS. 3 to 7, the respective bus bars 22 a, 22 b, and22 c are provided on their sides with respective terminal portions 50 w,50 u, and 50 v formed integrally together with the respective bus bars.The respective terminal portions 50 w, 50 u, and 50 v project outwardlyfrom the resin insulation layer 25. The respective terminal portions 50w, 50 u, and 50 v are connected through electric power source cables 51shown in FIG. 1 to a battery (not shown) for the thin DC brushless motor11. The respective terminal portions 50 w, 50 u, and 50 v are punchedout simultaneously when the bus bars 22 a, 22 b, and 22 c are punchedout from the conductive metallic plate by a press apparatus.Accordingly, the respective terminal portions 50 w, 50 u, and 50 v areformed integrally together as one-piece with the bus bars 22 a, 22 b,and 22 c, respectively, by a single pressing process. This can simplifythe production process in comparison with a procedure in which therespective terminal portions 50 u, 50 v, and 50 w are welded to therespective bus bars 22 a, 22 b, and 22 c.

[0085] As shown in FIGS. 6 and 7, the respective terminal portions 50 u,50 v, and 50 w are provided on the distal ends with bolt through-holesthat permit attachment bolts (not shown) for the electric power sourcecables 51 to pass. Resin-containing sections 53 are formed integrallytogether with the outer periphery of the resin insulation layer 25 toenclose the outer peripheries from the proximal ends to the centralportions of the respective terminal portions 50 u, 50 v, and 50 w. Theresin-containing sections 53 are filled with sealing material 54 made ofan insulative thermosetting resin. The sealing material 54 embedsportions disposed near the proximal ends away from the boltthrough-holes 52 and exposed from the resin insulation layer 25 on therespective terminal portions 50 u, 50 v, and 50 w. Waterproof-ness andairtight-ness functions are enhanced by the sealing material 54embedding the parts of the respective terminal portions 50 u, 50 v, and50 w. In the present embodiment, the sealing material 54 is preferably asilicone-based thermosetting resin. Alternatively, the thermosettingresin may be any resin other than a silicone-based resin.

[0086]FIG. 28 is a developed view of the bus bars 22 a, 22 b, and 22 c.As shown in FIG. 28, the respective terminal portions 50 u, 50 v, and 50w are disposed substantially on longitudinally central parts of therespective bus bars 22 a, 22 b, and 22 c. The numbers of the respectivetabs 41 a, 41 b, and 41 c on opposite sides of the respective terminalportions 50 u, 50 v, and 50 w are preferably the same. In more detail,three tabs 41 a, 41 b, and 41 c are provided on one side of therespective terminal portions 50 u, 50 v, and 50 w while three tabs 41 a,41 b, and 41 c are provided on the other side of the respective terminalportions 50 u, 50 v, and 50 w. The reason why the same numbers of thetabs 41 a,41 b, and 41 c are provided on the opposite sides of theterminal portions 50 u, 50 v, and 50 w is to permit equal amounts ofcurrent to flow in the tabs 41 a, 41 b, and 41 c.

[0087] As shown in FIGS. 6 and 8, the respective terminal portions 50 u,50 v, and 50 w include embedded sections 55 covered by the sealingmaterial 54 on their proximal ends, and exposed sections 56 having thebolt through-holes 52 and not covered by the sealing material 54 ontheir distal ends. The embedded sections 55 are pressed to form centralramp portions 55 a. These central ramp portions 55 a can save materialin comparison with central right-angled portions, and reduce weights ofthe bus bars 22 a, 22 b, and 22 c.

[0088] Slits 57 a and 57 b are provided on opposite sides of theembedded portions of the respective terminal portions 50 u, 50 v, and 50w. Both slits 57 a and 57 b extend in the longitudinal directions of therespective terminal portions 50 u, 50 v, and 50 w. The two slits 57 aand 57 b reduce a part of the embedded section 55, thereby making awidth of the reduced portion narrower than that of a non-reducedportion. Such structure can make a difference in reducing heatcontraction between the resin insulation layer 25 and the bus bars 22 ato 22 c when the resin insulation layer encloses the insulating holder25 during insert molding. The number and width of the slits 57 a and 57b may be changed without lowering mechanical strengths of the respectiveterminal portions 50 u, 50 v, and 50 w. For example, two slits 57 a and57 b may be provided on the opposite sides of the embedded section 55,respectively.

[0089] As shown by cross hatching in FIG. 8, parts of the exposedsection 56 and embedded section 55 on the respective terminal portions50 u, 50 v, and 50 w are covered by tinning. In more detail, tinningcovers an area from the distal end of the exposed section 56 to thecentral ramp portion 55 a of the embedded section 55. This tinning canprevent the bus bars 22 a, 22 b, and 22 c from being subject tocorrosion by oxidation.

[0090] After the respective terminal portions 50 u, 50 v, and 50 w arebent by a first press apparatus 60 shown in FIGS. 18 and 19, a secondpress apparatus 61 shown in FIG. 20 further bends them.

[0091] The first press apparatus 60 will be explained below withreference to FIGS. 18 and 19. As shown in FIGS. 18 and 19, the firstpress apparatus 60 bends the respective terminal portions 50 u, 50 v,and 50 w. The first press apparatus 60 includes a stationary lower diemember 62 and a movable upper die member 63. When the upper die member63 moves down toward the lower die member 62, both dies are closed.Conversely, when the upper die member 63 moves up away from the lowerdie member 62, both dies are opened.

[0092] The lower die member 62 is provided on the upper surface with alower forming V-shaped recess 62 a and a lower forming V-shapedprotrusion 62 b adjacent the recess 62 a. A pilot pin 64 is formed atthe top of the lower forming protrusion 62 b. When the pilot pin 64passes through a pilot hole 65 formed in the central ramp portion 55 aof each of the terminal portions 50 u, 50 v, and 50 w, the respectiveterminal portions 50 u, 50 v, and 50 w are positioned.

[0093] On the other hand, the upper die member 63 is provided on thelower surface with an upper forming V-shaped protrusion 63 a and anupper forming V-shaped recess 63 b adjacent the protrusion 63 a. Theupper forming protrusion. 63 a is opposed to the lower forming recess 62a while the upper forming recess 63 b is opposed to the lower formingprotrusion 62 b. When the upper die member 63 moves down toward thelower die member 62 to the closed position, the upper forming protrusion63 a engages the lower forming recess 62 a. The upper forming recess 63b is provided on the bottom surface with an escape recess 66. When thelower and upper die members 62 and 63 are driven to the closed position,the pilot pin 64 enters the escape recess 66, thereby preventing thepilot pin 64 and upper die member 63 from interfering with each other.

[0094] Next, a second press apparatus 61 will be explained below byreferring to FIG. 20. As shown in FIG. 20, the second press apparatus 61bends boundary sections between the respective terminal portions 50 u,50 v, and 50 w and the respective bus bars 22 a, 22 b, and 22 c. Thesecond press apparatus 61 comprises a stationary lower die member 67 anda movable upper die member 68. When the upper die member 68 moves downtoward the lower die member 67, both dies are closed. Conversely, whenthe upper die member 68 moves up away from the lower die member 67, bothdies are opened.

[0095] The lower die member 67 is provided on the upper surface with alower forming protrusion 67 a that engages the embedded section 55 onthe respective terminal portions 50 u, 50 v, and 50 w. An insertion pin69 is formed near the lower forming protrusion 67 a on the lower diemember 67 to position the terminal portions 50 u, 50 v, and 50 w. Whenthe respective terminal portions 50 u, 50 v, and 50 w are set on thelower die member 67, the insertion pin 69 passes through the respectivebolt through-hole 52. When the insertion pin 69 passes through the boltthrough-hole 52, the respective terminal portions 50 u, 50 v, and 50 ware prevented from being displaced.

[0096] The upper die member 68 is provided on the lower surface with anupper forming recess 68 a opposing the lower forming protrusion 67 a.When the upper and lower die members 68 and 67 are driven to the closedposition, the upper forming recess 68 a engages the lower formingprotrusion 67 a. The thickness of the portion of the upper die member 68other than the portion at which the upper forming recess 68 a is formedis designed so that the insertion pin 69 on the lower die member 67 doesnot interfere with the upper die member 68 when the upper and lower diemembers are driven to the closed position.

[0097] As shown in FIG. 18a and FIGS. 21A and 21B, a plurality ofnotches 59 extending in the lateral (width) direction are formed on theareas to be bent on the respective terminal portions 50 u, 50 v, and 50w by the first and second press apparatuses 60 and 61. Each notch 59 isformed in a surface of a strip-like blank 92 punched out from theconductive metallic plate before forming the respective terminalportions 50 u, 50 v, and 50 w. In the present embodiment, one notch isformed in one surface of the strip-like blank 92 corresponding to therespective terminal portions 50 u, 50 v, and 50 w, while three notchesare formed in the other surface of the blank 92. The strip-like blank 92is bent inwardly at the notch 59.

[0098] Next, a process for bending the respective terminal portions 50u, 50 v, and 50 w by using the first and second press apparatuses 60 and61 mentioned above will be explained.

[0099] As shown in FIGS. 18A and 18B, when the upper and lower diemembers 63 and 62 of the first press apparatus 60 are driven to theopened position, the strip-like blanks 92 punched out from theconductive metallic plate are put on the lower die member 62. The pilotpin 64 on the lower die member 62 passes through the pilot hole 65formed in a respective strip-like blank 92 to prevent or reducedisplacement of the blank 92.

[0100] As shown in FIGS. 19A and 19B, when the upper and lower diemembers 63 and 62 are driven to the closed position, the strip-likeblank 92 is clamped between the lower forming recess 62 a and the upperforming protrusion 63 a and between the lower forming recess 62 b andthe upper forming protrusion 63 b. Thus, the respective strip-likeblanks 92 are bent at the portions corresponding to the respectiveterminal portions 50 u, 50 v, and 50 w to form the respective terminalportions 50 u, 50 v, and 50 w. Thereafter, the upper and lower diemembers 63 and 62 are driven to the opened position and the strip-likeblank 92, in which the respective terminal portion 50 u, 50 v, or 50 wis formed, is removed from the lower die member 62.

[0101] As shown in FIGS. 20A and 20B, when the upper and lower diemembers 68 and 67 of the second press apparatus 61 are driven to theopened position, the respective terminal portion 50 u, 50 v, or 50 wformed by the first press apparatus 60 engages the lower die member 62.The insertion pin 69 passes through the bolt through-hole 52 formed inthe respective terminal portions 50 u, 50 v, or 50 w to prevent orreduce displacement of the blank 92.

[0102] When the upper and lower die members 68 and 67 are driven to theclosed position, an end of the strip-like blank 92, namely a portioncorresponding to the respective bus bars 22 a, 22 b, or 22 c, is clampedbetween the lower forming protrusion 67 a and the upper forming recess68 a to bend at a right angle the boundary areas between the respectivebus bar 22 a, 22 b, or 22 c and the respective terminal portion 50 u, 50v, or 50 w. Thereafter, the upper and lower die members 68 and 67 aredriven to the opened position and the strip-like blank 92, in which therespective terminal portion 50 u, 50 v, or 50 w is formed, is removedfrom the lower die member 67.

[0103] As shown in FIGS. 24 to 27, the resin insulation layer 25 forcovering the insulating holder 21 is formed by an insert-molding mold70. The insert-molding mold 70 comprises a stationary lower mold member71 and a movable upper mold member 72. The upper mold member 72 can moveto and from the lower mold member 71. When the upper mold member 72moves down to the lower mold member 71, the mold 70 is placed in aclosed position. When the upper mold member 72 moves up from the lowermold member 71, the mold 70 is placed in an open position.

[0104] A forming recess 71 a in the lower mold member 71 is opposed to aforming recess 72 a in the upper mold member 72. When the lower andupper mold members 72 and 71 are driven to the closed position, theforming recesses 72 a and 71 a define an annular cavity 73. A moltenresin material 90 is poured through a gate (not shown) into the cavity73 to form the resin insulation layer 25.

[0105] The upper mold member 72 is provided with upper mold membersupports 80 that push an upper surface of the insulating holder 21 to becontained in the cavity 73. The upper mold member supports 80 can moveout from and into an inner top surface of the upper forming recess 72 a.Although not shown in the drawings, a plurality of upper mold membersupports 80 (eighteen in the present embodiment) are provided in theupper mold member 72. The upper mold member supports 80 are arranged atan even spacing on the circumference of the insulating holder 21, exceptfor the portions where the terminal portions 50 u, 50 v, and 50 w arelocated. When the upper mold member supports 80 are advanced out fromthe upper forming recess 72 a, a plurality of latch grooves 81 formed inthe ends of the supports 80 engage the wall 43 b that spaces the insidebus bar 22 a from the intermediate bus bar 22 b, and also engage thewall 43 c that spaces the intermediate bus bar 22 b from the outside busbar 22 c. Under this engagement condition, distal end surfaces of theupper mold member supports 80 come into contact with upper end edges ofthe respective bus bars 22 a, 22 b, and 22 c. Consequently, the uppermold member supports 80 push the insulating holder 21 (an upper portionof the holder 21 in FIG. 24).

[0106] The lower mold member 71 is provided with holder support pins 74that support the insulating holder 21 to be contained in the cavity 73.The holder support pins 74 can move out from a bottom surface of thelower forming recess 71 a into the cavity 73 and move from the cavity 73into the bottom surface. Although not shown in the drawings, a pluralityof holder support pins 74 (thirty-six pins in the present embodiment)are provided in the lower mold member 71. The holder support pins 74 arearranged at an even spacing on the circumference of the insulatingholder 21. Each holder support pin is preferably formed into astick-like configuration having a tapered end. Preferably, the taperedend of each holder support pin 74 has a taper angle of about 30 to 150degrees.

[0107] As shown in FIG. 22, and FIGS. 23A and 23B, when the holdersupport pins 74 move out from the bottom surface of the lower formingrecess 71 a into the cavity 73, the distal ends of the pins 74 engagebearing recesses 75 in the lower surface of the insulating holder 21.This engagement can prevent displacement of the insulating holder 21 inthe radial direction of the cavity 73 when the insulating holder 21 iscontained in the cavity 73. The insulating holder 21 is fixed at aproper position in the cavity 73 by the holder support pins 74 and uppermold member supports 80. Consequently, the resin insulation layer 25 isformed around the insulating holder 21 at a uniform thickness.

[0108] Each bearing recess 75 has a taper that reduces the recess indiameter toward the inner top part. Thus, the holder support pin 74finally engages the bearing recess 75 while the pin 74 is being guidedalong the inner periphery of the bearing recess 75. Accordingly, whenthe insulating holder 21 is set in the lower forming recess 71 a in thelower mold member 71, the holder support pin 74 does not fail to engagethe bearing recess 75.

[0109] Two arcuate ribs 76 a and 76 b are formed around the holdersupport pin 74 on the bottom surface of the insulating holder 21. Theribs 76 a and 76 b make a virtual depth of the bearing recess 75 larger.This reduces the chance of the holder support pin 74 disengaging fromthe bearing recess 75 inadvertently and reduces the chance of theinsulating holder 21 displacing in the cavity 73.

[0110] A plurality of notches 77 a and 77 b (two notches in the presentembodiment) are formed between the ribs 76 a and 76 b . The formation ofthe notches 77 a and 77 b allows the resin for forming the resininsulating layer 25 to easily move toward the bearing recesses 75 viathe notches 77 a and 77 b in the state where the holder support pin 74is extracted from the bearing recess 75 during the processof insertmolding the resin insulation layer 25. In the centralized powerdistribution unit 17 in the final production step, the bearing recesses75 are filled with the resin insulation layer 25. The numbers of theribs 76 a and 76 b and the notches 77 a and 77 b can be arbitrarilychanged. When the ribs 76 a and 76 b are formed as one rib having aC-like shape, for example, the notches 77 a and 77 b can be configuredas one notch.

[0111] As shown in FIGS. 22, 23, and in FIGS. 14 to 16, the insulatingholder 21 is provided, in its bottom surface, with a plurality ofcommunication holes 78 communicating with the holding grooves 23 a, 23b, and 23 c. The communication holes 78 facilitate the flow of resin forforming the resin insulation layer 25 into the respective holdinggrooves 23 a, 23 b, and 23 c during insert molding. The pluralcommunication holes 78 are provided on the periphery of the insulatingholder 25. In more detail, the respective communication holes 78 arearranged along the holding grooves 23 a, 23 b, and 23 c. In addition, asshown in FIG. 10, the respective communication holes 78 are shifted fromeach other in the circumferential direction of the insulating holder 21.This means that only one communication hole 78 is disposed on the sameline in the radial direction of the insulating holder 21.

[0112] As shown in FIGS. 22 and 24, the insulating holder 21 is providedon the inner surface with positioning projections 82 the distal ends ofwhich come into contact with the inner surface of the lower formingrecess 71 a when the insulating holder 21 is set in the lower moldmember 71. The plural positioning projections 82 are arranged at an evenspacing in the circumferential direction of the insulating holder 21.When all of the positioning projections 82 come into contact with theinner surface of the lower forming recess 71 a, displacement of theinsulating holder 21 in its circumferential direction can besubstantially eliminated.

[0113] As shown in FIGS. 9, 12, and 13, the respective holding grooves23 a to 23 c in the insulating holder 21 are divided into a bus barcontaining section 83 that accommodates the bus bars 22 a to 22 c and abus bar non-containing section 84 that does not accommodate the busbars. First reinforcement ribs 85 are provided at a given distance inthe circumferential direction of the insulating holder 21 on the holdinggrooves 23 a, 23 b, and 23 c in the bus bar non-containing section 84.The respective first reinforcement ribs 85 are formed integrallytogether with bottom surfaces and inner side surfaces of the walls 43 ato 43 d. partitioning the respective holding grooves 23 a, 23 b, and 23c.

[0114] The communication holes 78 that serve to facilitate to flow themolten resin material 90 into the respective holding grooves 23 a, 23 b,and 23 c are formed in the bottom surface of the respective holdinggrooves 23 a, 23 b, and 23 c in the respective sections 83 and 84. Thus,the molten resin material 90 easily flows into the respective holdinggrooves 23 a, 23 b, and 23 c.

[0115] Three holding grooves 23 a, 23 b, and 23 c are provided in thebus bar containing section 83 in the insulating holder 21 while twoholding grooves 23 a and 23 b are provided in the bus bar non-containingsection 84 in the insulating holder 21. That is, there is no holdinggroove 23 c at the outermost side in the bus bar non-containing section84. The bus bar non-containing section 84 in the insulating holder 21 isnarrower than the bus bar containing section 83.

[0116] Furthermore, the bus bar non-containing section 84 in theinsulating holder 21 is provided on the outer periphery with a secondreinforcement rib 86 extending in the circumferential direction of theinsulating holder 21. The second reinforcement rib 86 is formed into anarcuate shape and a radius of curvature of the rib 86 is set to be thesame as the radius of the insulating holder 21.

[0117] Next, a process for insert-molding the centralized distributionunit 17 by using the insert-molding mold 70 described above will beexplained below.

[0118] When the mold 70 is driven to the opened position, the insulatingholder 21 is put in the lower forming recess 71 a in the lower moldmember 71. The holder support pins 74 projecting from the lower formingrecess 71 a engage the bearing recesses 75 in the insulating holder 21at the distal ends. Thus, the insulating holder 21 is supported in thelower mold member 71 with the holder 21 being spaced at a certaindistance from the bottom surface of the lower forming recess 71 a. Atthis time, the respective plural positioning projections 82 on theinsulating holder 21 come into contact with the inner periphery of thelower forming recess 71 a at the distal end surfaces. This substantiallyprevents displacement of the insulating holder 21 in the radialdirection.

[0119] As shown in FIG. 24, when the upper mold member 72 moves downtoward the lower mold member 71 to close the mold 70, the cavity 73 isdefined in the mold 70. When the mold 70 is closed, the distal endsurfaces of the upper mold member supports 80 projecting from the upperforming recess 72 a come into contact with the upper ends of the busbars 22 a, 22 b, and 22 c. Further, the latch grooves 81 in the distalend surfaces of the upper mold member supports 80 engage the walls 43 band 43 c that partition the respective holding grooves 23 a, 23 b, and23 c. Consequently, the upper mold member supports 80 push theinsulating holder 21 and the bus bars 22 a, 22 b, and 22 c. As describedabove, the insulating holder 21 is constrained from upward and downwardmovement by the plural holder support pins 74 and plural upper moldmember supports 80.

[0120] As shown in FIG. 25, molten resin material 90 for forming theresin insulation layer 25 is poured through a gate (not shown) formed inone of the mold members, e.g., the lower mold member 71, into the cavity73. At this time, the molten resin material 90 that is poured to coverthe insulating holder 21 flows through openings of the respectiveholding grooves 23 a, 23 b, and 23 c into their interiors. In addition,the molten resin material 90 flows through the communication holes 78 inthe insulating holder 21 into the holding grooves 23 a, 23 b, and 23 c.Even if the molten resin material 90 is applied.under pressure to theholding grooves 23 a, 23 b, and 23 c in the bus bar non-containingsection 84 (see FIG. 12) in the insulating holder 21, the first andsecond reinforcement ribs 85 and 86 prevent or reduce deformation of thewalls 43 a to 43 d.

[0121] When the molten resin material 90 substantially fills the cavity73, as shown in FIG. 26, the holder support pins 74 retract into thelower mold member 71 and the upper mold member supports 80 retract intothe upper mold member 72. Although the insulating holder 21 is fullyfloated in the cavity 73 without any supports, the insulating holder 21will not incline in the cavity 73 since the molten resin material 90 isbeing poured into the cavity 73. In addition, the molten resin material90 will fill the holes caused by the retraction of the holder supportpins 74 and upper mold member supports 80. Furthermore, the molten resinmaterial 90 flows into the bearing recesses 75 in which the holder.support pins have engaged, the spaces around the bearing recesses 75,and the spaces between and around the upper ends of the walls 43 b and43 c. Thus, the molten resin material 90 covers the insulating holder21.

[0122] As shown in FIG. 27, after a given period of time has passed andthe molten resin material 90 has cooled and solidified, the insulationlayer 25 is formed. Thereafter, the upper mold member 72 and the lowermold member 71 are separated and placed in the opened position, and thecentralized distribution unit 17, in which the insulating holder 21 andthe resin insulation layer 25 are integrated together, is removed fromthe mold 70.

[0123] An exemplary process for producing the centralized distributionunit 17 is explained below.

[0124] (Step of punching a conductive metallic plate)

[0125] As shown in FIG. 28, in order to form the bus bars 22 a, 22 b,and 22 c for a three-phase motor, three strip-like blanks 92 are formedfrom one rectangular conductive metal plate 91. In this case,the tabs 41a, 41 b, and 41c, and the terminal portions 50 u, 50 v, and 50 w arestamped out in a state where they are coupled to the respectivestrip-like blanks 92, by a press machine which is not shown.

[0126] As shown in FIG. 28, the strip-like blanks 92 which are stampedout from the conductive metal plate 91 are laid out along thelongitudinal direction of the conductive metal plate 91 so that they areparallel to one another. The two strip-like blanks 92 which arepositioned in the outermost side are placed so that the tabs 41 a and 41c and the terminal portions 50 v and 50 w are directed to the center ofthe bus bar row. According to the configuration, the three strip-likeblanks 92 can be densely laid out (laid out without forming large gaps)in the one conductive metal plate 91. As a result, the unused areasformed among the strip-like blanks 92 are narrowed. Therefore, theamount of wasted material is reduced, and the width of the conductivemetal plate 91 which is required for obtaining the strip-like blanks 92can be shortened.

[0127] The three strip-like blanks 92 are formed so as to have anapproximately same length. In the one conductive metal plate 91, thestrip-like blanks 92 are laid out so that their both ends aresubstantially aligned with one another. According to the configuration,in the one conductive metal plate 91, the unused areas formed in thevicinities of the both ends of the three strip-like blanks 92 arenarrowed. As a result, the amount of wasted material is reduced, and thelength of the conductive metal plate 91 which is required for obtainingthe strip-like blanks 92 can be shortened. Among the tabs protrudingfrom each of the strip-like blanks 92, the two tabs which are positionedat endmost portions are formed integrally with the end portions of thestrip-like blanks 92, respectively. Therefore, the lengths of thestrip-like blanks 92 can be shortened as compared with the case where,for example, a bus bar structure of a complete annular shape isemployed. This also contributes to the reduced length of the conductivemetal plate 91 which is required for obtaining the strip-like blanks 92.

[0128] In this way, the strip-like blanks 92 are produced from theconductive metal plate 91 before the bending process are applied to thebus bars 22 a to 22 c. Since the strip-like blanks 92 for forning thebus bars 22 a, 22 b, and 22 c have a substantially linear shape as shownin FIG. 29, they can be stamped out in parallel. This remarkablycontributes to a reduced material cost, and to an improved yield ascompared with the case where the strip-like blanks 92 are annularlystamped out.

[0129] (First bending of the bus bars)

[0130] As shown in FIG. 29, the first and second press apparatuses 60and 61 mentioned above bend the portions corresponding to the terminalportions 50 u, 50 v, and 50 win the strip-like blanks 92.

[0131] (Second bending of the bus bars)

[0132] As shown in FIG. 29, the portions corresponding to the bus bars22 a, 22 b, and 22 c in the strip-like blanks 92 in which the terminalportions 50 u, 50 v, and 50 w have been formed are bent in the thicknessdirection to form annular shapes. This bending work is carried out by abending device (not shown). Thus, the bus bars 22 a, 22 b, and 22 c areformed into substantially annular shapes beforehand, before attachingthe bus bars 22 a, 22 b, and 22c to the insulating holder 21.

[0133] (Step of inserting the bus bars)

[0134] As shown in FIG. 30, the respective bus bars 22 a, 22 b, and 22 care inserted into the insulating holder 21 that has already beenproduced. At this time, the bus bars are inserted into the insulatingholder 21 in order from the outermost position to the innermostposition. That is, the outside bus bar 22 a, intermediate bus bar 22 b,and inside bus bar 22 c are inserted into the insulating holder 21 inthat order. If the inside bus bar 22 c is inserted into the insulatingholder 21 before inserting the intermediate bus bar 22 b, the prior busbar interferes with entrance of the latter bus bar.

[0135] (Third bending of the bus bars)

[0136] As shown in FIG. 31, the respective tabs 41 a, 41 b, and 41 c arebent so that their distal ends are directed to the center of theinsulating holder 21 with the respective bus bars 22 a to 22 c beingattached to the insulating holder 21. The curved portions 44 and 45 areformed on the proximal ends of tabs of the the intermediate bus bar 22 band outside bus bar 22 c, respectively.

[0137] (Insert molding)

[0138] As shown in FIG. 32, the resin insulation layer 25 is formed onthe outer periphery of the insulating holder 21 to which the bus bars 22a, 22 b, and 22 c have been already attached. This forming process maybe carried out by using the insert-molding mold 70 mentioned above.Thereafter, the centralized distribution unit 17 is taken out from theinsert-molding mold 70. Finally, the sealing material 54 fills the resincontaining sections 53 (FIG. 5) formed in the resin insulation layer 25.

[0139] Accordingly, effects including the following effects may beobtained according to the above-described embodiment.

[0140] (1) The bus bars 22 a, 22 b, and 22 c are formed by stamping outinto a strip-like shape from the one conductive metal plate 91. In thiscase, the bus bars 22 a, 22 b, and 22 c are stamped out from theconductive metal plate 91, in the state where the bus bars are denselylaid out. Therefore, the required area of the conductive metal plate 91can be made smaller than that in the case where the bus bars 22 a, 22 b,and 22 c are stamped out into a ring-like shape. Consequently, thematerial loss is reduced as compared with that in a conventional method,so that the material cost of the bus bars 22 a, 22 b, and 22 c can belowered. As a result, the centralized power distribution unit 17 can beeconomically produced.

[0141] (2) The bus bars 22 a, 22 b, and 22 c are simultaneously stampedout from the common conductive metal plate 91 by using a mold. In thiscase, the used area of the conductive metal plate 91 can be reduced toabout a half of that in the case where the bus bars 22 a, 22 b, and 22 care stamped out into a ring-like shape, and the material loss isreliably suppressed. Therefore, the material cost of the bus bars 22 a,22 b, and 22 c can be reduced. Unlike the conventional art, it is notrequired to use different molds for respective rings. Therefore, themold cost can be reduced. As a result, the centralized powerdistribution unit 17 can be more economically produced.

[0142] (3) The tabs 41 a, 41 b, and 41 c, and the terminal portions 50w, 50 w, and 50 v are integrally formed, coupled with the bodies of thebus bars 22 a, 22 b, and 22 c, respectively. In this case, it is notnecessary to attach the tabs 41 a, 41 b, and 41 c, and the terminalportions 50 w, 50 w, and 50 v in a subsequent step by welding or thelike. Therefore, the number of steps of producing the bus bars 22 a, 22b, and 22 c can be reduced. As a result, the centralized powerdistribution unit 17 can be more economically produced.

[0143] (4) The bus bars 22 a, 22 b, and 22 c are stamped out from theconductive metal plate 91 in the state where both ends of the bus barsare substantially aligned with one another, and in the state where thebus bars are placed in parallel. In the conductive metal plate 91,therefore, material loss in the areas of the ends in the longitudinaldirection and the sides in the width direction of the bus bars 22 a, 22b, and 22 c is reduced. Consequently, the material cost of the bus bars22 a, 22 b, and 22 c can be further lowered, so that the centralizedpower distribution unit 17 can be still more economically produced.

[0144] (5) Among the bus bars 22 a, 22 b, and 22 c, the bus bars 22 aand 22 c which are positioned in the outermost side are laid out inparallel so that the terminal portions 50 w and 50 v and the tabs 41 aand 41 c are directed to the center of the bus bar row. According tothis configuration, in the conductive metal plate 91, the material lossin the areas of the ends in the longitudinal direction of the bus bars22 a, 22 b, and 22 c is reduced. Consequently, the material cost of thebus bars 22 a, 22 b, and 22 c can be further lowered. As a result, thecentralized power distribution unit 17 can be still more economicallyproduced.

[0145] The above-described embodiment of the invention may be modifiedin, for example, the following ways.

[0146] In the above-described embodiment, the terminal portions 50 w, 50u, and 50 v, and the tabs 41 a, 41 b, and 41 c are formed integrallywith the bodies of the bus bars 22 a, 22 b, and 22 c, respectively.Alternatively, the terminal portions SOw, 50 u, and 50 v, and/or thetabs 41 a, 41 b, and 41 c may be formed by stamping as members separatedfrom the bodies of the bus bars 22 a, 22 b, and 22 c. For example, asshown in FIG. 33, the bus bars 22 a, 22 b, and 22 c are laid out inparallel. The terminal portions 50 u, 50 v, and 50 w are laid out inparallel with the bodies of the bus bars 22 a, 22 b, and 22 c, betweenthe tabs 41 a, 41 b, and 41 c disposed on the bodies of the bus bars 22a, 22 b, and 22 c. According to the configuration, the bus bars 22 a, 22b, and 22 c can be placed more densely, and hence the amount of wastedmaterial in the width direction of the conductive metal plate 91 isfurther reduced. Therefore, the area of the conductive metal plate 91which is required for stamping out the bus bars 22 a, 22 b, and 22 c canbe made smaller than that in the above-described embodiment. In thiscase, the terminal portions 50 w, 50 u, and 50 v, and the tabs 41 a, 41b, and 41 c are later attached to the bodies of the bus bars 22 a, 22 b,and 22 c. As a method of conducting the later attachment, specifically,welding, brazing, soldering, screw fixation, or the like may be used.

[0147] In the above-described embodiment, the terminal portion 50 w, 50u, or 50 v, and the tabs 41 a, 41 b, or 41 c are formed on the same sideedge of the corresponding one of the bus bars 22 a, 22 b, and 22 c.Alternatively, the terminal portion 50 w, 50 u, or 50 v, and the tabs 41a, 41 b, or 41 c may be formed on different side edges.

[0148] In the above-described embodiment, the invention is applied tothe centralized power distribution unit 17 for the three-phase thin DCbrushless motor 11. The invention is not limited to this, and may beapplied to a centralized power distribution unit for a motor in whichthe phase number is larger than three (or smaller than three). Inaccordance with the phase number, the numbers of the bus bars and theholding grooves may be increased or decreased.

[0149] In this case, for example, four bus bars for a four-phase motormay be stamped out from a common conductive metal plate 91, or five busbars for a five-phase motor may be stamped out from a common conductivemetal plate 91.

[0150] In addition to the technical concepts explicitly described above,several technical concepts can be grasped from the embodiment describedabove. The technical concepts will be described together with theireffects.

[0151] (1) In a method of producing bus bars used in a centralized powerdistribution unit, the terminal portion and the tabs are formed on asame side edge of the bus bar body. According to the configuration, thestamping can be performed so that the terminal portion and the tabs ofone(s) of the bus bars which are positioned in the outermost side amongthe bus bars which are placed in parallel are directed to the center ofthe bus bar row. Therefore, the material loss in the process of stampingout the bus bars from the conductive metal plate can be reduced, so thatthe centralized power distribution unit for a vehicular thin brushlessmotor can be produced at a low cost.

[0152] As described above in detail, according to the invention, it ispossible to provide a centralized power distribution unit for avehicular thin brushless motor which can be produced in a relativelysimple manner, and which has high reliability.

[0153] According to the invention, the material cost of the bus bars,and the mold cost can be reduced, and hence the centralized powerdistribution unit for a vehicular thin brushless motor can be producedat a low cost.

[0154] According to the invention, the number of steps of producing thebus bars can be reduced, and hence the centralized power distributionunit for a vehicular thin brushless motor can be produced at a low cost.

[0155] According to the invention, the loss of the metal material forproducing the bus bars can be further reduced, and hence the centralizedpower distribution unit for a vehicular thin brushless motor can beproduced at a lower cost.

[0156] While the invention has been described in conjunction with thespecific embodiments described above, many equivalent altematives,modifications and variations may become apparent to those skilled in theart when given this disclosure. Accordingly, the exemplary embodimentsof the invention as set forth above are considered to be illustrativeand not limiting. Various changes to the described embodiments may bemade without departing from the spirit and scope of the invention.

[0157] The entire disclosure of Japanese Patent Application No.2001-330026 filed on Oct. 26, 2001 including the specification, claims,drawings and summary is incorporated herein by reference in itsentirety.

What is claimed is:
 1. A method of producing a centralized powerdistribution unit for a vehicular thin brushless motor wherein saidcentralized power distribution unit is formed into a ring configurationand can concentratedly distribute current to stator windings of themotor, the method comprising: stamping out a conductive metal plate intoa plurality of strips, the strips stamped out simultaneously by pressmolding; bending the strips in a thickness direction into asubstantially annular shape to obtain a plurality of bus bars in theform of rings, the rings being mutually different in diameter, the busbars each having a terminal portion to be connected to a power sourceand one or more tabs to be connected respectively to one or morewindings of the motor; providing the bus bars correspondingly withphases of the motor; stacking the strips in a radial direction of thecentralized power distribution unit, mutually separated by apredetermined gap; and covering the bus bars with a resin insulatinglayer.
 2. A method of producing bus bars, comprising stamping out aconductive metal plate into a plurality of strips, the strips stampedout simultaneously by press molding; and bending the strips in athickness direction to obtain a plurality of rings, the rings beingmutually different in diameter.
 3. The method of producing bus barsaccording to claim 2, wherein, in the step of stamping out, at least oneof (a) a terminal portion and (b) one or more tabs are integrallystamped with a main body of the bus bar.
 4. The method of producing busbars according to claim 3, wherein, in the step of stamping out, the busbars are stamped out in a state where the main bodies are laid out inparallel, and in a state where both ends of the main bodies aresubstantially aligned with one another.
 5. The method of producing busbars according to claim 2, wherein, in the step of stamping out, aterminal portion and one or more tabs are integrally stamped with a mainbody of the bus bar.
 6. The method of producing bus bars according toclaim 5, wherein, in the step of stamping out, the terminal portion andthe one or more tabs of a predetermined one of the bus bars are laid outto be directed to a center of a row of the bus bars, the predeterminedone of the bus bars being positioned at an outermost side among the busbars which are placed in parallel.
 7. A method of producing acentralized power distribution unit wherein said centralized powerdistribution unit is formed into a ring configuration and canconcentratedly distribute current to stator windings of a motor, themethod comprising: stamping out a conductive metal plate into aplurality of strips, the strips stamped out simultaneously by pressmolding; bending the strips in a thickness direction to obtain aplurality of rings, the rings being mutually different in diameter; andstacking the strips in a radial direction of the centralized powerdistribution unit mutually, separated by a predetermined gap.
 8. Themethod according to claim 7, wherein each bus bar includes a terminalportion that connects to a power source, further comprising bending theterminal portion into a bent configuration.
 9. The method according toclaim 8, wherein bending at least one of the terminal portions comprisesbending the terminal portion such that the at least one of the terminalportions includes a first section extending in a first direction that isa substantially radial direction of the centralized power distributionunit, a second section extending in a second direction substantiallyperpendicular to the first direction, and a ramp section connecting thefirst and second sections and extending in a third direction that isdifferent from the first and second directions.
 10. The method accordingto claim 8, further comprising providing at least one slit in at leastone of the terminal portions.
 11. The method according to claim 10,further comprising a section of the at least one of the terminalportions by a sealing material, wherein the at least one slit isprovided in the section covered by the sealing material.
 12. The methodaccording to claim 10, wherein the at least one slit extends in alongitudinal direction of the terminal portion.